Tainted
by Kishoto
Summary: Sakura knew she would never be worthy of him. She would never be worthy of anyone. Not with her spoiled body.


**Fair warning. This story is…very dark. To say the least.**

 **But darkness has its own place in this world. It is only through its contrast that we can see light.**

* * *

Sakura sat in her room at a worn desk, an English textbook open in front of her. She was poring over it, occasionally glancing back at her notebook and adding a word or two, when there was a knock at her door. Her pencil stilled.

The knock came again and Sakura stood abruptly, walking over to the door. She put her hand on the knob, but didn't turn it. She didn't want to see who was on the other side. It could only be one of two people, and Sakura would rather see neither.

The knock sounded a third time, unfailingly polite, and Sakura gripped the knob. If it had been Shinji, he would've grown impatient and opened the door himself, assuming he'd bothered to knock in the first place.

"Sakura-chan. Are you awake?"

It was a pointless question, they both knew it. There was nothing in the Matou household that escaped Zouken's notice, least of all his favorite grandchild's actions.

"I'm afraid it's time for your chores. Come now, the sooner you start, the sooner you can be finished, _ne_?"

Chores. As if he was calling Sakura to sweep the den or wash the dishes. Maybe he thought he was being funny?

Sakura opened the door, enough to see her grandfather's hunched visage. His haggard appearance was offset by his black, dead eyes, which were alive with experience and twisted cunning, born of centuries living a cursed half-life.

"I understand, ojii-sama. If it wouldn't be too much trouble, may I finish my homework assignment first? It's due in the morning and I'm always rather…tired after chores."

Zouken smiled at his kin, the expression benign and kind to anyone who didn't know the truth.

"Of course, precious granddaughter. Please, feel free. I'll wait downstairs."

Sakura fought back her urge to sigh in relief, as her grandfather stepped away and started walking down the hallway, and went to close her door. She'd bought herself a brief respite, an hour at best, before she would have to attend to her duties. It wasn't much but it would-

"Oh, Sakura-chan?"

She paused, the barest crack between her door's edge and the wall. She stared at it, as if willing it to do what she couldn't, and close in on itself, shielding her from whatever her grandfather was about to say.

"I know that your schoolwork is very important. But duty to your family should always be first and foremost."

Her heart quickened as she felt prana start to surge around her grandfather. The worms in her blood reacted, roused from their slumber and she opened her door, frantically rushing out and bowing before her grandfather, back straight.

"I apologize, ojii-sama! I'll come with you right away. So…please…"

Her plea hung in the air, unspoken but apparent. She waited, facing the ground, as the worms continued to wake up, shortening her breath and causing her legs to shake.

A few more seconds passed, after which she felt the prana emission from her grandfather ebb. The Crest Worms inside her body slowed, falling dormant once again, and she sighed, silently, as her breathing started to return to normal. She dared not rise before given permission however, and held her pose.

A minute passed, before she felt a hand under her chin, cold and clammy despite the summer heat. She followed its direction and found herself looking into the face of Zouken Matou. His eyes were closed, as he smiled softly at his heir.

"Your courtesy pleases me, Sakura-chan. I admire the commitment you have to our family and its noble lineage." She smiled, praying that her face betrayed none of her trepidation, "However your sincerity is still lacking, despite all that we have done for you."

Sakura froze, the smile slipping as Zouken opened his eyes, and she stared into the depths of insanity and purpose that was the head of the Makiri. He clutched her chin, a cruel strength held within its brittle grip.

" **Vas ren**."

Zouken's prana surged outwards, over twice as large as before, and the worms within Sakura Matou sprung awake, jarred violently from their sleep. She fell to her knees, wrapping her hands around herself, for all the good it did her. A scream tried to force itself through her lips but she grit her teeth, releasing only a series of whimpers.

Fire sprung up inside of her heart, before rapidly spreading outwards, her nerves dancing in agony as the worms fed on her prana. With each heartbeat, the sensation spread, the worms gorging themselves on the essence of the young woman that was their host.

She fought down the urge to scream again, as she felt the heat blossom from between her legs and radiate outwards, just as painful, but accompanied by a familiar blast of shame and revulsion. She gripped her knees, willing the worms to settle as she breathed in short, brief pants. She urged her prana to flow, cycling throughout her body, to feed the worms that resided in her blood.

She felt the fire fade, ever so slightly, as the worms started to slow down, having had their fill. They continued eating, but she could endure this. The worst was over, she could handle this pain. She'd gotten used to it a long time ago.

" **F** **ï** **o**."

Sakura's breath hitched and she looked up, with wide eyes. She said nothing, but it was clear that she was silently pleading with the aged magus.

But pleading rarely stopped your average magus. Let alone Zouken Matou.

His prana spiked once again, and she felt all of the pain vanish suddenly, as if a light switch had been turned off, and she gasped,

"No…"

Her voice was soft, broken. Tears had started to collect in her eyes, prompted by the lack of pain where the fire in her veins had previously provoked none.

Sakura felt it start, as it always did, at her womanhood. A warm heat, akin to what she'd felt before, but different. Smaller. And bereft of any pain. No, this was a heat borne of pleasure.

The worms inside of her responded to this, keening softly as they drank in the sensation. They moved almost affectionately, as they used the prana in their systems to broadcast this message back out, the signals overlapping with what was already present, the resultant pulse being twice as strong as what it was imitating.

Sakura gasped, as she felt the sensation start to spread. Slow and gentle, where the fire had been fast and rough. Her cheeks heated, an iridescent red in the darkness, as her breathing quickened for much different reasons than it had before. She squeezed her knees together, trying to ignore the dampness she could feel between her thighs.

The rising crescendo of pleasure made the well of tears in her eyes increase, threatening to spill over and stain her cheeks with their saline presence. She clutched at her chest, bending over as she tried to stay still, every movement only adding to her impending arousal.

Her nipples started to harden despite her efforts, and their insistent presence against her arms caused the dam to break, as she let out a choked sob as she put her face into her hands. She hated being this way. She hated being this…this _freak_ , made to feel pleasure under the torturous presence of these disgusting creatures.

The pleasure only continued to rise, slow but insistent in its path, as she felt her body start to warm in a way she'd grown sickeningly familiar to. Her breaths grew shorter and shorter, as the worms skittered eagerly, the carnal impulses of their host almost as satisfying to them as prana, the magical essence that gave them form.

She was dripping now, she could feel it. What had been a slight dampness had now become a veritable flood that showed no signs of stopping, bypassing the panties she wore as if they weren't even there. She clasped her hands, resisting the desire to caress her nipples and touch herself through the soaked fabric, the pleasure at war with an equal sense of shame and guilt.

 _Senpai…_

The thought only made her feel even more ashamed. She wasn't worthy of any man, let alone her beloved upperclassman. She was spoiled. Tainted. Her place was at the feet of the Matou family, and that's where she would stay. She deserved nothing more.

"Oh, well isn't this a familiar sight."

Sakura heard the footsteps, and looked up into the face of her brother, Shinji. She felt an irrational hatred spring up inside her, before she dampened it down. She had no right to hate her brother. She'd stolen what was his, and his treatment of her was the only way he had to feel in control. She knew this, and forgave him for it.

"Gomen…nii-san. I apologize for waking you…"

Sakura's words were short and clipped, punctuated by heavy breathing and her constant shifting.

"You didn't wake me, Sakura. I was just out for a stroll, stretching my legs when Grandfather found me, and informed me that you may need my assistance getting downstairs."

She wanted to believe him. She hoped that really was all that Shinji was here to do, but one look at his face told her otherwise. His eyes were half lidded, and stared into hers with undisguised intentions. She felt the warmth inside of her react, and she crossed her arms, attempting to hide her body's reaction to his gaze. Her breathing grew even shorter as she looked at his crotch, where a bulge had made itself noticeably apparent against the loose confines of his pajama bottoms.

She gulped and looked away, cursing herself for her desire and her cowardice.

"It's…it's fine, nii-san. I am more than capable…your kindness is appreciated, _arigatou_."

Normally, any denial from Sakura would instantly set Shinji off, but this was a game they'd played before, and he knew it was one that was rigged in his favor. His grin widened, and he leaned down, gently gliding his hand across Sakura's shoulder.

She gasped, shrinking from the contact, as what felt like little lightning bolts, _wonderful lightning bolts_ , flowed directly from her shoulder to her crotch. She would've almost thought her brother had used magecraft, if she didn't know for a fact that he didn't possess a single Magic Circuit.

"I'm afraid I must insist. It wouldn't do for me to leave you in such a state, _nee-chan_."

Sakura bit her lip, pressing her back to the wall of the hallway as if she could pass through it by sheer force of will. Shinji didn't acknowledge her as his sister. In any form. He only called her sister in these moments, these painfully ironic moments when they did things a real brother and sister should never do.

His hand traveled down her shoulder, Sakura flinching with each inch as it traveled down her arm. He grabbed her hand gently, almost lovingly, before raising it to his face. He examined her fingers idly, before blowing softly on her index finger.

"Ah…"

Sakura's voice escaped, more a moan than anything resembling speech as the nerves in her hand sparked and danced, the worms greedily responding to the stimulation the young, talentless Matou provided. She cried out further as Shinji's lips gently surrounded her finger, sucking on it lightly and raking it with his teeth.

The hallway was heavy with the scent of female arousal, as Sakura panted, watching her brother suckle her finger as if it was a piece of hard candy. She wanted to pull her hand away, to shove her brother away and reprimand him for his actions, the way she would Senpai when he'd do something stupid, or foolish. But she couldn't.

She told herself it was because this was her brother, the one she'd stolen everything from, who was simply hurt and lashing out at her because she was there. She told herself she deserved to offer him what little comfort she could in exchange, no matter how shameful.

But Sakura knew. She'd never been good at hiding how she felt from herself, as much as she hid what she felt from others, and she knew that she didn't refrain from reprimanding Shinji for his sake. She refrained because her body was shameless and dirty, and it was making its desires known. It wanted Shinji to do more than suckle one little finger.

She looked up, her eyes locking with Shinji's as he smiled around the captive digit, his tongue flicking out and swiping at it, playfully. He could read her desire like an open book; he'd grown quite familiar with it over the years. He released the finger and eyed its slick surface.

"Nii-san…"

Sakura's voice was soft, but heavy, the word barely coming out of her as she fought an internal war against both herself and Zouken's familiars. A war she knew she'd lose, but would fight anyway.

"Oh, what is it Sakura? Is something the matter?"

Shinji wanted to burst into laughter. He probably would've, if it wouldn't have clashed terribly with the caring, older brother routine he was putting on.

"I…just…"

Each word was a struggle. Sakura clutched her hands to her chest, her heart beating hard against her palms. She wanted to tell him to leave, to go to bed, but there were parts of her that fought, eager for something else, something Shinji was usually all too willing to provide.

"I'm sorry, what was that? I'm going to need you to speak up, nee-chan."

Shinji's grin was light and easy, but his eyes were heavy, and the bulge below his waist had only grown during his ministrations to the purple haired girl before him. She averted her eyes, her hands tracing her breasts unconsciously, seeking an outlet. Any outlet.

She thought of Senpai, and she felt the urge to cry return, held at bay by the much more demanding urges she was forced to contend with. She wished she could talk to him, to tell her that it wasn't her fault. That she didn't want to be like this. She didn't want to be a broken, lustful doll.

"You're thinking about him again, aren't you?"

Shinji's voice had dropped, losing all levity. Sakura's gaze snapped back, and she saw the darkness in her brother's gaze, aided by the frown set into his features. This look was different. Before, Shinji's look hadn't been kind, to be certain, but it hadn't been so overtly hostile. There'd been lust and playfulness in equal measure, but no ill intent.

Now, that playfulness had been exchanged for something dark, something that was innately Shinji Matou. A feeling of hatred and rage, spawned by an inferiority complex a decade strong. It wanted to lash out and teach Sakura her place. Which was firmly below his.

He reached out, grasping Sakura's hair and twisting it, roughly. A cry escaped her lips, but it was one of arousal, not pain. The wave of pleasure that Sakura had been riding took in the impulses and twisted them, more carnal sustenance for the Crest Worms inside of her, which only led to her feeling more pleasure.

Shinji made a mockery of a smile and laughed, pulling again, eliciting a longer moan this time.

"You're such a slut, Sakura! I'm practically pulling the hair off your head and all you can do is whine like a bitch in heat!"

Sakura wanted to refute him, but she knew it wouldn't help. And it wouldn't be true. Her brother was right. She was no better than a dog as she was now.

He dragged her to her feet, and she cried out again, the feel of pulling at her scalp only heightening her dangerously high level of sexual frustration.

Using his other hand, Shinji roughly palmed her breast, the contact sending a shock through her, as she screamed, the pleasure spiking as she quivered, her entire body aflame. Her knees shook as she felt her brother's hand grasp and massage her chest. Her head was spinning, and she felt dizzy, the wall behind her supporting her more than her own legs at the moment.

Shinji leaned in, cheek to cheek with her and he inhaled.

"I've missed this, nee-chan."

His voice had slipped back into his kind façade, its falsity made apparent by the way he gripped her hair even tighter.

"You smell so good. I always loved you, you know..."

He would always do this. He would tell her he loved her in these moments. And it would make her grieve, because she knew he didn't mean it. He didn't love her at all. He loved what her body was oh so ready to do for him.

His hands traced her breast, tenderly now, finding her nipple. He grazed it gently, once. Then twice. Each contact causing Sakura to arch into him just a bit more. Finally, with no preamble, his hand lashed out, grabbing and twisting the peaked nub, his grip far too tight to be pleasurable to any normal woman.

But Sakura was anything but normal, and the sudden spike of pain, followed by the even greater spike of arousal caused her to scream, a high piercing note as she felt her entire body peak, reaching a conclusion it had been working towards for the past several minutes. She arched into Shinji, riding her climax as she ground against him, his laughter lost to her ears as she felt even more fluid burst from between her thighs, spraying forward in droplets over Shinji's clothed legs.

Sakura couldn't think. Couldn't speak. All she could do was feel every single part of her body alight in the shamefully pleasurable fire that was solely her own. For all that it was provoked by the Matou familiars within her, she knew that this pleasure belonged to her and she couldn't bring herself to feel any guilt over it as she started coming down from her climax.

She came to, eyes blinking as the room came back into focus, the first thing she saw being her brother's purple gaze, set in that familiar smug expression she'd grown accustomed to seeing after coming by his hand countless times.

"Well, did you have fun, nee-chan?"

His voice was playful again, but the mocking edge to it was very real. He knew exactly what he'd done, and he reveled in it, in the power he held over the one who'd stolen his lineage from him.

Sakura looked down as she searched for the shame and guilt she'd felt only seconds before. As usual, they were gone, shut into a part of Sakura that didn't seem able to coexist with herself after reaching such a peak. The emotions would return, she knew, all too soon, but they were currently drowned out by the pleasure she could still feel, slumbering briefly, but building itself up again, as it hungered for more.

Her empty gaze locked onto Shinji and she reached out, her hand barely grazing Shinji's thigh before he stepped back, laughing.

"Now, now nee-chan. You know the rules!"

Sakura did. She knew what Shinji wanted her to do, and HE knew that this was the only time he could get her to consent to this, when she was… **this**. This thing that was less than human, less even than the real Sakura Matou, spoiled as she was.

She would regret her actions, once she was allowed to feel human again, after she was done satisfying both herself and Zouken's familiars. She'd probably cry, feeling dirty and ashamed, cursing her diseased body for its repeated betrayals.

But that was a problem for the Sakura of the future. The Sakura of right now was unable to bring herself to care.

Sakura stood, barely a tremor belying her heated state as her hands rose, unbuttoning her shirt with almost mechanical efficiency. It fell to the floor, followed by her bra, releasing her breasts to the world.

Shinji's gaze perched on her left breast, where red marks, evidence of his abuse stood out, bright against her pale skin. He licked his lips as he watched Sakura fiddle with her skirt, before letting it fall to the floor.

She stood before him in a pair of cotton panties. Their white fabric was rendered practically transparent by the juices coating them, allowing Shinji an unobstructed view of Sakura's labia, crowned by a small tuft of violet hair.

"Shinji-sama…."

Sakura's voice was soft and pleading, vulnerable. Shinji had worked long and hard over the years to instill that tone in her, and didn't mind that it still rang hollow, even though it sounded like the perfect rendition of a humble servant addressing its master.

Sakura reached to her waistband, pulling her panties down and stepping out of them, clutching them loosely in her left hand. The scent of arousal in the air spiked, growing even more apparent than it had been before.

Sakura raised the fabric to her nose and breathed in, the heavy blush on her face growing darker as she smelt the physical evidence of her lust. Her tongue darted out and swabbed over the fabric, and she moaned as she tasted herself, the soft tanginess spreading across her taste buds and arousing her further.

"Hah! Look, nee-chan, you're leaking again!"

Shinji's voice was steeped in lust and petty mockery as he watched the fluid run down her legs, the trails of liquid leaving shiny tracks on her thighs. His arrogance was such that, even now, he interpreted such things as signs of her honest desire for him, as opposed to the mindless, prana fueled madness it actually was.

"Come on, nee-chan, I haven't got all night. Get to the next part!"

Sakura dropped the underwear, standing before Shinji naked, her eyes blank but her cheeks bright red, as she panted. She got down onto her knees and crawled over to him, looking up at him as if he was her Master.

"Please, Shinji-sama. I need you."

More fake words, a part of the script he'd forced onto her years ago. Both of them knew this, and neither of them cared.

Shinji laughed, throwing his hands in the air.

"Who am I to deny my lovely little nee-chan what she wants?"

He grabbed Sakura by her wrist, hauling her none too gently to her feet. He caressed either side of her face briefly, before pulling it towards him and kissing her.

It was a kiss that was all raw force and passion, and Sakura responded instantly, her tongue crashing against his as she ran her hands over his body, knowing just the way he liked to be touched.

Her hands roamed, caressing that spot on his lower back that made him shiver and kiss her even harder as she prodded it through his thin shirt. She moaned as his mouth moved down, suckling at the base of her neck, where faded remnants of their past activities could be perpetually found. There was a reason she didn't wear anything without a button-capable collar.

Shinji pulled back, his breathing matching Sakura's as he stared into her eyes. If he tried, really tried, he could convince himself that what he saw in there was love for him, instead of baseborn lust driven by his grandfather's familiars. He didn't NEED Sakura's love, of course, but it stroked his ego to think that, even after all the years he'd spent forcing himself on her, she had fallen in love with him.

Without a word, he pulled her down the hall, unconcerned with her nakedness. Shinji knew that his Grandfather knew what they were doing, and would leave them to it. After passing a few doors, they stopped at a particular one and Shinji opened it, walking inside. Sakura plodded after him obediently.

Shinji quickly divested himself of his sleepwear, his pale chest standing out against the dark color scheme of his room. His erection stood straight, more than adequately primed by Sakura's earlier displays. Sakura had already walked over to the bed, standing by it, all too aware of what Shinji wanted.

Shinji practically pranced over, taking a small leap and landing on his bed, lying on his back, with his cock jutting proudly into the air.

"You know the drill, Sakura-nee-chan." He whispered teasingly, giving Sakura his best smoldering look. She didn't react to it at all, except to simply climb onto the bed, swinging one knee over Shinji so that she straddled him, his swollen manhood barely grazing her slick entrance. She felt the desire in her well up even further, expectant of what was to come.

She idly searched for the shame and guilt that she knew, on some level, she should be rightfully feeling, but only found more arousal, and she surrendered herself to it. She arched up, grabbing Shinji's cock with practiced ease, before aiming it and sliding down onto it in one smooth motion.

The Matou siblings groaned simultaneously, the familiar union setting off a shared conflagration of sexual pleasure. Sakura wasted no time and started moving her hips, riding Shinji with an ease that she would have found disgusting if she had the capacity to.

She moved up and down, his penis moving inside of her in smooth thrusts that left her panting with desire she couldn't, and wouldn't, restrain. She felt like one large nerve ending, solely stimulated by the cock she had nestled in between her legs. It wasn't the largest, but it also wasn't small. And it felt good. It did its job more than adequately, as Sakura's moans could attest to.

Shinji had his eyes closed and was panting, his hands at his side fisting the coverlet. Some part of him ached to reach out and touch Sakura, to hold her and guide her movements, but an even larger part of him gloated, reveling in her complete subservience to him, making him too prideful to reach up and show any modicum of affection.

Instead, his hands lashed out, and grabbed her waist, forcefully stopping her motion. He felt her walls quiver, the sudden stop jarring and unwanted as she gave out a soft, disappointed noise, almost cat like.

Shinji breathed in and out, getting his bearings as he smirked up at his sister, who looked down at him in both annoyance and resignation. After all, this was part of the rules as well, and Shinji's pride wouldn't let him continue without making sure she acknowledged it.

"Well, nee-chan? Something to say?"

Sakura panted, her breasts heaving as she looked down at Shinji, seeming conflicted. Even in her lust driven state, where all feelings of shame and guilt were firmly ousted, she found the control to hate herself for this. For what Shinji wanted her to say.

Regardless, the flames were insistent. And it only took seconds before Sakura wistfully thought of her treasured Senpai, before putting him too, in the mental box that held everything that was Sakura Matou, outside of this sinful pleasure.

"Shinji-sama…your cock is…superior."

Shinji smiled, releasing Sakura's hips, allowing her to resume her previous motion, but at a much slower pace.

"Hmm, is it now? Superior to whom, my darling nee-chan?"

Sakura panted, averting her eyes as she still found the dregs of her pride and shame shackling her. She continued her motions, picking up speed, hoping to subdue Shinji with her body. But Shinji's pride was no fickle thing and his hand lashed out, catching her on the cheek.

She continued, the pain minute compared to what she suffered at Grandfather's command, before she felt a second and a third slap. Her cheeks were an even brighter red, now, but still. Three times nothing is nothing. Her motions were unabated, as she felt the familiar sensation start to flare up, cresting even more rapidly than it had before.

Sakura sped up even further, her moans growing louder as she felt her climax approaching, only for her to be forcefully grabbed and thrown, Shinji's cock slipping out of her with a wet _plop_ as she hit the bed beside him. He turned over, holding her wrists down, his cock poised at her entrance.

He looked down at Sakura again, eyes filled with rage and perceived insult. He clearly wanted nothing more than to lash out and take his anger out on her, but he knew she wouldn't care. Over the years, he'd slapped her, punched her, kicked her. He'd even once gotten daring and pushed her down the stairs. He'd done everything his Grandfather would allow, and she bore it all with that infuriatingly calm smile, forgiving him for each and every misstep.

No, nothing he could do to her physically would hurt her. She was much too inured to pain by the worms. So, he'd learnt to cheat. He learnt to use those very same worms to his advantage, like right now. He knew Sakura was close to her release, he could easily see the signs after all these years, and he'd stopped before she could get there. Because she wasn't following the fucking rules, and she should know better by now.

Shinji released her wrists and merely kneeled over her, his cock poised to enter her. He made no motion, however, and simply waited. He knew what would happen next. It was inevitable.

Sakura looked up at him, furious in her own right, squirming underneath him. She tried to reach her hands down, but he merely slapped them away, preventing her from reaching below their waists. Her hands clutched at her breasts, angrily tweaking her pink nipples, her arousal rising but clearly not spiking in that familiar way.

She kneaded helplessly, knowing it was pointless, but praying that this time, out of all the other times, might be different, but she knew she was getting nowhere. So she looked up at Shinji, and felt her resentment flare up against him. For once, she didn't fight it. She allowed herself, for a few brief minutes, to well and truly hate Shinji Matou.

Tears welled in her eyes as she thought about him, about those warm brown eyes, and his dusty orange hair. She wished she could be someone else, someone that wasn't enslaved to her body's darkness. Someone that was worthy of him, who could walk alongside him and love him, and feel like she was worth being loved in return.

"Shinji-sama…your cock is much superior to Senpai's…he cannot match you…"

Sakura had never slept with Shirou. She'd never even kissed him. And when Shinji had started his sick little games, that's what she'd told him, time and again. But he never believed her. He couldn't wrap his head around a girl spending so much time at a guy's place, where he lived alone, without sex being a factor.

It had gotten to the point where he would tie Sakura up, binding her wrists and ankles to his bed, leaving her to stew. Her arousal and desire would rise with no outlet, brought along by his teasing fingers, to the point where she wasn't able to even think. To a point where, if she'd stayed much longer, she was sure she'd never be herself again. So she lied. She told Shinji she did sleep with him. He'd hit her, and yelled at her, and called her a bitch and a cunt for thinking she could deceive him.

' _Is my cock better than Emiya's? Tell me my cock is better than Emiya's! Tell me!'_

He refused to fuck her or release her until she did. So what could she say, but yes? She'd begged and pleaded but finally, with tears running down her face, she said yes. After that simple, three letter word, Shinji had come at Sakura like an animal, all fury and passion. He was invigorated by the dominance he had over his perceived rival, happy to finally have something over the boy that was taking away his sister, bit by bit.

They had gone at it for hours, surpassing their previous session time limits by leaps and bounds. Sakura had never known she could feel that way, she'd never been desperate enough to fully submit herself to her tainted body's desires. But that day, she did. And she found that she could never go back to what they were doing before. She felt the depths of her desire and arousal in new ways that frightened her and made her physically ill to think about, despite the fact that she found herself unable to resist them. Shinji was the only one she had to attend to the insistent sin that was her body's craving, and he knew it. She needed him.

"Oh, is it now? I'm afraid I'm not very convinced, Sakura…"

Shinji started to pull away, but he felt his sister grab him around his waist. He smiled inwardly, looking down at her with a bored expression that was fooling no one.

"He can't match you. Comparing your cock to Emiya's is like comparing the sun to the moon."

She felt Shinji edge closer, but no further, his cock head dangling tantalizingly between her outer lips.

"He's much smaller. And doesn't last nearly as long. I couldn't enjoy myself at all…"

She could feel Shinji's cock head kissing her entrance now. He was almost convinced. She looked up at him, and felt tears rise to her eyes, unbidden. Their appearance only made Shinji smile wider, because it made him know he was hurting her. What he did here was doing more than any insult or slap ever could. And he loved it. He didn't even care if she was telling the truth anymore, he just knew he loved to see those tears run down her perfect, little, forgiving face.

He leaned down, whispering softly in her ear, "Come on nee-chan. Tell me how you really feel."

"You're the only man that could ever hope to satisfy me, Shinji-sama. You and you alone."

With a cry of victory, Shinji plunged forward, the rapid insertion causing Sakura to arch below him, eyes wide as she felt the dam within her finally burst, as the shock rode straight from the tips of her toes to the top of her head. Her muscles quivered uselessly as they were overridden by the prana fueled sexuality of her orgasm, and she fell limply onto the bed spread, mewling helplessly as Shinji kept selfishly plowing her, unmindful of her orgasm, and the sensitivity therein.

His carelessness brought another climax right on the heel, and Sakura saw spots as she arched again, fingers scrabbling uselessly over Shinji's back as he kept going, heedless of Sakura's wellbeing. As far as he was concerned, she was his toy. His property. To use, abuse and throw away, as he so desired.

As he forged ahead to his own orgasm, Sakura felt her own arousal start to wane, and it terrified her. She knew what was coming. She knew what awaited her after this. She didn't fear the worms that she would be fed too, once again. She feared herself. She feared the return of the proper Sakura Matou, and all the human emotions she contained.

She feared the crushing weight of her shame and guilt as she had to face the love she felt for Shirou with yet another stain on her already darkened soul. She feared that, one day, she would find that she was unworthy of even being his friend, and just stop seeing him altogether. She was scared that her actions would hurt the real Sakura Matou, the one she locked away to sate her own selfish desires, to a point that she wasn't able to come back from. She feared being stuck like this, in a body that could do nothing but crave sex.

But most of all, she feared one thing, the one thing that would consume her mind in the days to come, the thing that Shinji always brought up as he lay next to her when they were done with... **this**. When she was starting to come back to her real self, and he was sated from his desire for her body.

Shinji leaned over and nipped at her ear, grabbing it roughly between his teeth, and he saw her back away, instead of moan. Eye him with sad eyes, instead of lustful ones. Sakura's desires had run their course and she knew that he knew this now, and was only waiting to be sure he had her full, sober attention.

Shinji leaned in, and put his lips near to her ear

"You know, maybe one day I'll tell Emiya about this. About all of it."

It was not the first time Shinji had made the threat. It wasn't even the tenth. But Sakura's heart clenched all the same and she found herself saying the same thing she'd said a dozen times before.

"Please, nii-san…don't."

As he always did, Shinji smiled and looked down at her, at the tired, sad eyes of his adopted sister, for once consumed by her own, selfish desires instead of that damnable pitying look she always gave him. The sight made him happy, and he patted his sister's cheek, the gesture more condescending than affectionate.

"Hmm….fine. Maybe next time."

With that, Shinji flipped over, yawning as he grabbed at the coverlet. His foot reached out, shoving Sakura off the bed. She caught herself with practiced ease and stood, wobbling, a familiar soreness already starting to make itself apparent, her arms reaching over in a futile attempt to hide her body from her brother's sleepy, roving gaze.

"Now, get out of my room. Grandfather still wants to see you, and he's already gonna be pissed you're late."

Shinji spoke as if it was entirely her fault, as if he was completely innocent of having anything to do with her tardiness, but Sakura was used to it. She walked over to the door, opening it and switching off the light. She started to exit, closing it behind her, before looking back and softly saying,

"Goodnight nii-san."

Shinji didn't hear her, already asleep. But he wouldn't have cared, even if he had, so the effect was much the same. Sakura closed the door softly, before looking down the hall. Her clothes were strewn about where she'd tossed them, along with a rather unsightly wet spot. The air in the hallway still hung heavy with stale, female arousal. She tilted her head at the mess, before turning around and heading towards the foyer on slightly unsteady legs, navigating her way to the basement stairs in familiar darkness.

After all, she still had chores to do.


End file.
